This tart will fit into a 9? round perfectly. If you want to use a rectangular tart like pictured, you will end up with a wee bit extra filling. Use the extra crust and filling to make a mini tart or two in a ramekin.
- 113 grams (1 stick) cold unsalted butter
- 210 grams (1½ cups) all-purpose gluten-free flour (I prefer Cup4Cup)*
- ½ teaspoon xantham gum**
- 5 grams (1 teaspoon) granulated sugar
- ½ teaspoon salt
- 1 large egg yolk
- ¼ cup buttermilk***
- 2-3 medium sweet potatoes, cut into ¼ inch slices
- 6 sprigs of thyme with the leaves pulled off and the branches discarded
- 2 tablespoons of olive oil
- generous sprinkling of coarse salt & fresh ground pepper
- 1¼ cup heavy cream
- 1 egg
- 115 grams (about 1¼ cups) finely grated parmesan cheese
- ¼ cup roughly chopped fresh sage
- Cut the butter into fourths and place in a food processor. Add the flour, sugar and salt. Pulse until you have a mixture that is the texture of wet sand.
- Add the egg yolk & butter milk. Pulse until just combined.
- Gather the dough up, press it into a disc about 4? in diameter. Wrap it in plastic and place it in the refrigerator. You can do this up to 24 hours before you want to make the tart.
Make the filling
- Line a rimmed baking sheet with parchment paper & preheat the oven to 350 degrees Fahrenheit.
- Peel & slice the sweet potatoes into ¼inch thick slices. (Slice them one at a time and guage how many you need – drop them into your tart pan and see how full it gets, when it is mostly full, you have enough just in case we have very different ideas about what a medium sweet potato is)
- Lay them out flat and drizzle with olive oil, and sprinkle with thyme, salt and pepper. It is important that you don’t skip seasoning the potatoes.
- Bake them for 15-20 minutes. You want them to just be softening.
- In a small bowl, lightly beat the egg and cream together.
Assemble the tart
- Raise the oven temperature to 375 degrees Fahrenheit, and place a clean baking sheet on the middle rack of the oven.
- Take the dough out of the freezer, and on a well floured surface, roll it out to be 2? wider and longer than your tart pan.
- Gently lift the dough and pace it into the tart pan. Press the dough into the edges and fix any tears with extra dough.
- Line the bottom of the tart pan with sweet potato slices and top with ¼ of the parmesan cheese and then ¼ of the sage. Repeat 2-3 more times (until you run out of potatoes).
- Slowly and carefully pour the egg and cream mixture over the potatoes and cheese. Be patient, it has to seep all around your potatoes to fill in all the air pockets.
- Top with any remaining parmesan and sage.
- Place the tart pan on top of the hot baking sheet in the oven. Bake for 40-45mins. When the crust is lightly browned and the cheese is golden and bubbly, your tart is done.
- Let cool for 10 minutes before removing the tart from the pan to allow the filling to set up.
*Frankly, I think Cup4Cup works the best of any of the blends you can currently purchase. Jules Nearly Normal and Better Batter are suitable alternates if you can’t have dairy or can’t find the Cup4Cup in your area. **If you use any of the commercial blends I mentioned, you won’t need this, but if your flour blend doesn’t contain any gums, expandex or other binding agent, you will need this ***If you don’t have buttermilk use the following: 3 tablespoons + 2½ teaspoons heavy cream and ½ teaspoon vinegar. Combine and let sit for 5 minutes before starting
Courtesy: Mary Fran Wiley, Frannycakes
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